Polarization maintaining optical fiber interferometer capable of simultaneously measuring strain and temperature

Abstract

The invention provides a polarization maintaining optical fiber interferometer capable of simultaneously measuring strain and temperature. The system comprises a narrow-band light source, a total polarization-maintaining Mach-Zehnder interferometer, an interference signal detection unit, a differential circuit and a demodulation system. A polarization-maintaining optical fiber device is adopted toconstruct a full-polarization-maintaining interferometer, and the optical signals are simultaneously transmitted in the fast axis and the slow axis of the polarization maintaining optical fiber, andtwo sensing systems are formed. The two sensing systems have different responses to the temperature and the strain respectively, so that simultaneous measurement of the two can be realized. The Mach-Zehnder interference structure does not have back-reflection transmission, and rayleigh scattering noise in the light transmission process is effectively inhibited. Light in the polarization maintaining optical fiber is separated from the fast and slow axes, the differential circuit is used for carrying out differential processing on the coaxial signals, the noise is reduced, and the measurement precision is improved. The polarization maintaining optical fiber interferometer is simple to manufacture, convenient to measure, high in precision and capable of effectively overcoming the problem of cross sensitivity. The polarization maintaining optical fiber interferometer can be applied to the fields of oil exploration, and seismic observation.

Description

technical field [0001] The invention relates to an optical fiber sensing technology, in particular to a polarization-maintaining optical fiber interferometer for simultaneous measurement of high-precision strain and temperature. Background technique [0002] As one of the important research contents in today's sensing field, fiber optic sensor has the advantages of small size, light weight, high sensitivity, large dynamic range, anti-electromagnetic interference, and ability to work in harsh environments. The application of fiber optic sensors in environmental measurement is also becoming more and more extensive. [0003] Since optical fibers are affected by strain and temperature at the same time, and the two interfere with each other, how to separate the two factors of strain and temperature and realize the simultaneous measurement of the two has become a hot spot in research and development. At present, the optical fiber sensors that can be applied to the simultaneous me...

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Problems solved by technology

[0007] In 2009, Li Aiqun of Southeast University and others proposed to package two fiber gratings with different responses to strain and temperature into a stainless steel tube, and then measure strain and temperature (CN201382778Y). The general problem of this method is the structural Complex, bulky, and there is a certain distance between the two sensing structures, the large error leads to low measurement accuracy; therefore, the gradual replacement of the above method is to actively produce two different response structures in a set of sensing devices. Sensing unit

In 2012, Song Zhangqi of the University of National Defense Science and Technology of the Chinese People's Liberation Army disclosed a method for simultaneously measuring strain and temperature by obtaining fiber gratings with different diameters by etching (CN102829893A), which is to make two different features on the same optical fiber. The grating makes it respond differently to strain and temperature, but this method will introduce additional losses and reduce the performance of the sensor, and active fabrication will also have the problem of uncontrollable accuracy

[0008] In 2011, Koji Omichi, Sakura (JP) et al. disclosed a physical quantity measurement device using optical frequency domain reflectometry and a method for simultaneously measuring strain and temperature using the device (US7889332B2). This method utilizes In order to realize the characteristic that the fast and slow axes of polarization-maintaining fiber work at the same time, a double-Michelson interferometer was built with the help of the sensing performance of the grating, and the strain and temperature of the detection position were determined by the OFDR analysis method and the wavelength change of the Bragg reflected light. High spatial resolution, multi-point measurement and other advantages, but the demodulation algorithm is relatively complicated, the grating needs to be fabricated, and the technical cost is relatively high

The sensor has a simple structure and is convenient for measurement, but it is measured according to the wavelength change of the valley in the transmission spectrum, the dynamic range is small, and the welding is relatively complicated

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